The costs of asphaltic material and other petroleum based products have steadily risen. Current conventional asphalt roofing shingles 500 shown in FIG. 1 include a saturated fiberglass or organic mat 502, a top layer of asphalt coating 504 on the exposed surface 506, a bottom layer of asphalt coating 508 on the unexposed surface 510 of the saturated mat, a surface layer of granular material 512 applied over the top layer asphalt coating 504 on the exposed surface 506 (some of which may be colored), and a layer of fine granular material 514 on the unexposed surface 510 to cover the bottom layer of asphalt coating 508. The layer of granular material 512 on the exposed surface 506 provides the wearing surface of the shingle and a corresponding visual appearance of the shingles. The layer of fine granular material 514, which may include mineral or non-organic aggregate, on the unexposed surface 510 keeps the shingles from sticking together when stacked for packaging and transport.
As the prices of asphaltic material used to coat asphalt shingles and the costs for transporting the manufactured shingles continue to increase, a reduction in the weight of an asphalt roofing shingle due to removal of asphaltic materials provides many useful benefits. Such benefits may include (1) making it more affordable by reducing the amount of non-weathering surface asphaltic material required to produce a shingle, (2) making it more efficient to transport the shingles from the manufacturer to the job site, and (3) making installation easier as crews handle and install the lighter-weight shingles.
Moreover, the fine granular aggregate material used to coat the unexposed surface is expensive, especially when purchased and used in high volume, as in the roofing shingle manufacturing process. Using sand and these other aggregate backing particulates also creates waste as more backing material is applied than necessary to ensure complete coverage of the surface. In addition, the fine particulates in the aggregate, which often include sand, are generally abrasive and penetrate the manufacturing equipment and their abrasive edges cause serious wear and tear to the rollers, drums, gears and other mechanisms associated with the equipment. As will be appreciated, the repair and replacement of manufacturing equipment is expensive. Further, the use of fine aggregate particulates typically requires use of conventional engineering controls and sometimes personal protective equipment to control both personal exposure to employees and emissions to the environment of silica or other dusts.
Thus, there is a need in the art for lightweight shingles having substantially the same or improved performance characteristics when compared to conventional asphalt shingles. There is a further need in the art to provide a shingle which eliminates the use of the fine aggregates or granular material applied to the back surface to reduce the cost of manufacture and to protect the manufacturing employees from being exposed to the fine aggregate dusts and particulates, while also providing substantially the same or improved performance characteristics when compared to conventional asphalt shingles.